The Prospect of the Electroless Atomic Layer Deposition (ALD) for Applications in Semiconductor Technology

The metallic thin films are widely used for in semiconductor technology. Surface morphology, thickness and purity of the film are the key attributes determining its functionality ^1,2. Recent developments indicate that Cu/liner/TaN structures where liner could be either Co, Ru or Rh and TaN serves as barrier are of particular interest. The electrochemical doping of Zn with liner material to develop barrier-less Cu structures has been demonstrated³. In this talk we demonstrate a protocol to deposit conformal Cu thin film on Co by replacement of Zn overlayer without etching Co. EDTA and BTA are used for corrosion inhibition of Co film once all Zn capping layer is consumed in galvanic displacement with Cu. TEM, XPS and EDS indicate conformal Cu layer deposition Co layer underneath being intact. The second part of the talk focuses on electroless ALD application for deposition of Pt and Rh layers on Cu, Au or Ru substrates. ^4,5. Surface reflectivity changes during electroless ALD serves as an indicator of surface roughness evolution after each cycle. Surface morphology after 20 electroless ALD cycles is studied by STM and AFM. Cyclic voltammetry illustrates catalytically active Pt and Rh surface after deposition. All electroless ALDs are performed at room temperature in glove box with inert atmosphere. Surface selective, self-terminating deposition and precise control over the film thickness are achieved demonstrating potential of this deposition method for scale up and industrial applications.

1. Ahmadi, K., Wu, D., Dole, N., R. Monteiro, O. & R. Brankovic, S. Tuning Surface Chemoresistivity of Au Ultrathin Films Using Metal Deposition via Surface-Limited Redox Replacement of the Underpotentially Deposited Pb Monolayer. ACS Sensors 4, 2442–2449 (2019).

2. Wu, D. et al. Pb Monolayer Mediated Thin Film Growth of Cu and Co: Exploring Different Concepts. Journal of The Electrochemical Society 166, D3013–D3021 (2019).

3. Kailash Venkatraman, Yezdi Dordi, A. J. Electrochemical doping of thin metal layers employing underpotential deposition and thermal treatment. 1 (2019).

4. Wu, D. et al. Electroless Deposition of Pb Monolayer: A New Process and Application to Surface Selective Atomic Layer Deposition. Langmuir 34, 11384–11394 (2018).

5. Wu, D. et al. Underpotential and Electroless Pb Monolayer Deposition on Ru(0001). Journal of The Electrochemical Society 166, D359–D365 (2019).

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